Magnetic nanoparticles have potential applications in optics, electronics, micro-electronics, aerospace, biomedicine and other fields. For example, magnetic nanoparticles are often used as contrast enhancing agents for magnetic resonance imaging (MRI) systems (See e.g. Mornet et al., “Magnetic nanoparticle design for medical diagnosis and therapy,” J. Mater. Chem., 2004, 14, 2161-75).
Magnetic nanoparticles are typically used in conjunction with a solid support structure, matrix or solid phase material. In at least one application disclosed in the prior art, nanoparticles are integrated into a solid phase. Several solid hosts, such as mesoporous silica (See e.g. Zhang et al., Chem. Mater., 2002, 14:1965) and carbon nanotubes (See e.g. Liu et al., Chem. Mater. 2000, 12:2205) have been used as templates for the growth of metal nanoparticles.
Alternatively, pre-formed nanoparticles may be deposited or otherwise coated onto the surface of a solid phase or matrix. Several issues may arise when coating a matrix using pre-formed nanoparticles. First, the coating methods used may not be compatible with the matrix, which is to say the matrix may not maintain its structural integrity and physical properties throughout the coating process. Further, depending on the coating methods and the solvent used, the nanoparticles may not adhere to the matrix with the necessary degree of affinity. Also, it may be very difficult to achieve uniform dispersion of the nanoparticles when coating a matrix with pre-formed nanoparticles. Non-uniformity may lead to inconsistent physical, electrical and/or chemical properties along the surface area of the coated matrix. There is, therefore a need for a coating method, that overcomes one or more of the problems discussed above.
Furthermore, because the magnetic property of a nanoparticle depends on the size and shape of the particle, there is also a need for a method to effectively control the size and shape of the nanoparticles being coated onto the matrix. Although Ung et al. demonstrates the correlation between particle size, shape and various reaction conditions (Adv. Mater. 2Q05, 17:338-44), no methodology has been established to control the size, shape and magnetic properties of magnetic nanoparticles in the context of in-situ matrix coating.
Hence there is a need for a material and method of manufacturing to address one or more of the drawbacks identified above.